Escorcia, S. P. Texas A & M University, susie@ocean.tamu.edu
MacDonald, I. P. Texas A & M University, ian@gerg.tamu.edu
Joye, S. B. University of Georgia, mjoye@arches.uga.edu

 
SPATIAL AND INTER-ANNUAL VARIATION OF SULFIDE FLUXES IN CHEMOSYNTHETIC COMMUNITIES IN THE GULF OF MEXICO
 
Rich chemosynthetic macrofaunal communities at hydrocarbon seeps in the Gulf of Mexico are supported by the activity of chemoautotrophic microorganisms that couple the oxidation of methane or sulfide with the fixation of inorganic carbon into organic biomass. The connections and feedbacks between microbial activity and the geochemistry of these communities are not fully understood. We assessed the role of geochemistry in fueling microbially mediated processes by estimating sediment-water interface fluxes of sulfide (S2-), manganese (Mn2+) and iron (Fe2+). Sediment cores were collected from bacterial mats and tubeworm colonies using the submersible, Johnson Sea Link, in July 1997 and 1998. Profiles of reduced constituents were obtained using solid state Hg-Au amalgam microelectrodes, which permit simultaneous measurements of O2 and reduced S, Fe, Mn at millimeter intervals. Gradient-driven fluxes of S2-, the dominant reduced species, for the top centimeter of sediments for the two sampling periods for bacterial mats ranged from -825 to -3016 in 1997 to -132 to -5810 micromol/m2 day in 1998 and for tube worm colonies ranged from 0 to 1306 micromol/m2 day in 1997 to below detection in 1998. Spatial and inter-annual variations in S2- fluxes provide insights to the mechanisms controlling the distribution of these communities.
 
Day: Tuesday, Feb. 2
Time: 09:30 - 09:45am
Location: Sweeney Center
 
Code: SS27TU0930S